Assessment of a High Temperature Refractory-lined Suspension Flow Solar Particle Receiver

Abstract

The use of ceramic particles, alone or in suspension within an air stream, as a heat transfer medium is one of the current focussed areas for the development of high temperature receiver-based concentrated solar thermal technologies. These solid particle receiver systems have the potential to achieve operating temperatures of >1000◦C, which is typically required for high temperature industrial processes. This requires the use of either expensive high temperature metals or linings of refractory, which is both brittle and has high thermal inertia. While the refractory is a proven material used in high temperature furnaces, limited information is available on the use of refractory linings in solar receivers while accounting for transient thermal input. Hence there is a need to better understand the thermal behaviour of these high temperature refractory-lined particle receivers considering their response to solar transients during start-up, turn down and shutdown periods. Also, the use of air as the heat transfer fluid for retrofit applications in industry arises the need to understand the system-level performance of these receivers, when operating in combination with sensible thermal storage, while accounting for the true variations in the returned thermal inputs from the process. To meet these needs, this thesis reports on the thermal performance and optimization of a refractory-lined suspension-flow windowless vortex receiver for a solar thermal particle technology used to generate high temperature air. These assessments are made with a transient mathematical model developed to calculate the heat and mass transfer within the cavity of a Solar Expanding Vortex Receiver (SEVR) together with the thermal losses to the surroundings, incorporating the influence of solar transients during start-up, turn down and shutdown periods. New insights are provided of the influences of the variables of refractory configuration and of the potential operating controller parameters to manage the influence of solar variability. Further to this, new understandings are provided on the system level performance of a refractory-lined SEVR operating in combination with a packed bed sensible thermal storage, and other components of a complete concentrated solar thermal plant. Overall, the results show that it is possible to size a refractory lining appropriately to allow reliable operation under the transient and cyclical conditions of a solar receiver. This offers advantages in terms of cost and efficiency. The results also provide insights of a strong dependence of the overall system performance on the interaction between the individual sub-systems, indicating the importance of carefully sizing the sub-systems in combination rather than in isolation for retrofit industrial applications. The findings also show how to optimize refractory lining for such conditions which makes it relevant to other types of high temperature receivers, to integrate and simulate different system types, and to assist in identifying which type of system is best suited to which application, when accounting for start-up, turndown and shutdown losses.